engleski

Exploring the Stoichiometric Diversity and Mechanochemical Reactions of Halogen-Bonded Cocrystals

Solid-state studies havebeen fundamental for the understandingof halogen bonding, with crystallography as the most important tool. Particularly, cocrystallization has offeredinsight into the influence of varyingdonors and acceptors on the halogen bond properties. Other interactions, such as weak C−H hydrogen bondsand aromatic ring stacking can also compete with halogen bonding. Using di-or multi-topic halogen bond donors and acceptors often gives rise to cocrystals comprising same components in different stoichiometric ratios –stoichiomorphs, as not all donor/acceptor sites necessarily engage in halogen bonding. Moreover, polymorphism can also complicate the structural landscape of even a very simple halogen-bonded cocrystal system. Mechanochemistry is anefficient, rapid cocrystallization screening method. Avoiding solubility issues, two or more coformers can be directly transformed into a cocrystalof thedesiredstoichiometry. Furthermore, cocrystals of different stoichiometries can be easily interconvertedby the addition of the respective coformer and grinding. In our work, we focused on a set of simple bromine-or iodine-based halogen bond donors and nitrogen-based acceptors. Their cocrystallization was studied by neat or liquid- assisted grinding, with varying milling times and stoichiometric ratios. State-of-the-art periodic DFT calculations were used to establish the relative stabilities of different phases. Mechanochemical screening revealed the remarkablephase diversity inthe studiedsystems. Whilethe coformer ratiowas found to reliably determine the stoichiometryof the final products, different stoichiomorphs and polymorphs were observed as intermediatesduring mechanochemical cocrystallization. DFT calculations were successfulinpredictingthe final products, with entropic contributionsemergingas critical for stabilizingsome of the obtained cocrystals.

halogen bond ; cocrystals ; mechnanochemical reactions

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